@gocheed90
Actually that law only applies to depiction of actual children, meaning if the characters are based off an actual person then it's illegal. However since artist can of course claim every character as being purely fictional creations they again remain legal.

It's actually a bit convoluted, as if you read Title 18, 2252A which gocheed's link refers to for the penalty and regards the possession, distribution, etc. of -real- child pornography, section (c)(2) states

"(c) It shall be an affirmative defense to a charge of violating paragraph (1), (2), (3)(A), (4), or (5) of subsection (a) that—

(2) the alleged child pornography was not produced using any actual minor or minors. "